Habitat: On rocks, perennial, throughout intertidal, often as flattened rosettes covering exposed rocks, also subtidal, generally distributed, abundant.Similar species:Osmundea osmunda is very similar but arises from a discoid holdfast, and is generally lower down on the shore and larger, with isolated plants. Osmundea truncata is much less common, is more pinnately branched, generally grows epiphytically, and rapidly degenerates on collection.Key characteristics: Stoloniferous holdfast, smaller thanOsmundea osmunda , and less profically branched.